1. Field of the Invention
This invention relates in general to sliding door units. More particularly, this invention relates to an improved sill for such a door unit which serves to support the stationary and movable door panels of the door unit.
2. Description of the Prior Art
Sliding door units are well known. One particular type of sliding door unit is that which is known as the Andersen Perma-Shield.RTM. Gliding Door. The Perma-Shield.RTM. Gliding Door unit is a door unit for use generally adjacent a patio of a house or other structure. This door unit includes a door frame or casing and two door panels. The door panels contain a glazing which comprises a double paned safety insulating glass. One of the door panels is fixed inside the frame. The other door panel slides relatively thereto to open and close the door opening in the door unit. When the door panels are in their closed position (i.e., the door opening is closed), the innermost frame members of each door panel, which are called the meeting stiles, are located generally adjacent one another and are spaced apart by a small gap.
Prior art sliding door units have had sills formed with various configurations. One particular type of sill has comprised an aluminum sill member having downwardly extending mounting projections. These projections were received in saw slots in a wooden framing member on which the sill was mounted. Furthermore, the prior art sill was divided into two parts: (1) a first inner portion which would underlie the movable door panel and have formed thereon the means for guiding the movable door panel during its sliding movement, and (2) a second outer portion positioned to the exterior of the inner portion and forming a threshold on which the person going through the doorway opening from the outside would step. These inner and outer sill portions were separated by a vinyl barrier.
One problem with the prior art sill construction noted above is that as people stepped on the threshold of the sill it would often tend to fracture the sill or separate the outer sill portion from the vinyl barrier. When the sill became cracked, this would require replacement which is an expensive and inconvenient procedure. In addition, if the sill became cracked and detached from its framing members, this would allow water to infiltrate into the interior of the structure in which the door unit was mounted. More particularly, one common problem in such units was that water often infiltrated in the gap between the stationary and movable door panels. This problem could be particularly acute in a heavy or driving rain storm because the construction of the prior art sills was not specifically designed to alleviate this problem of water infiltration.
Prior art sliding door units made some provision for supporting that portion of the sill which formed the outer or exterior threshold. Conventionally, the support was accomplished merely by securing a two-by-four to the front face of the framing member on top of which the sill was mounted. This two-by-four would be positioned to abut up against the bottom of the outer threshold. As people entering the building stepped on the threshold, the threshold and their weight would be supported by this two-by-four piece of lumber. Although such a sill support is generally effective for supporting the threshold, certain disadvantages are presented by the use of a piece of lumber for the sill support. One primary disadvantage is that the size of the lumber must usually be cut to different widths if the openings in which the sill was mounted had different thicknesses. Thus, when the framing members defined an opening having a relatively large thickness, a two-by-four positioned beneath the threshold might extend out past the edge of the threshold. This would require that the two-by-four be cut until it was flush with the threshold edge. The fact that no single sill support could accommodate various sized thicknesses in the opening for the door unit is a disadvantage as time and labor must be expended in cutting the prior art sill supports to size.
In the manufacture of sliding door units it is often difficult to adequately guide and secure the stationary door panel in the door frame. This problem is accentuated because the door panels are large, bulky and also quite heavy which makes them extremely hard to handle. To the best of applicant's knowledge, there has been no completely satisfactory method for guiding the permanent door panel into its proper assembled position during the manufacture thereof. The lack of such a system has made the task of manufacturing such door units more difficult. This increases the expense of manufacturing the unit and the expense to the purchaser in buying the unit.